1. Field of the Invention
The present inventions relate to steering control systems for boats including an electric steering drive system.
2. Description of the Related Art
A conventional electric steering control system for an outboard motor is described in Japanese Patent Document JP-B-2959044. In the device, the rotation or pivoting of a steering wheel or handle is detected by a sensor. The sensor sends a signal to a controller. Using this signal, the controller drives an electric motor which in turn, changes the steering angle of the outboard motor to thereby steer the boat in accordance with the movement of the steering wheel or handle. The controller is configured to change the steering angle of the outboard motor by a predetermined amount based on the detection of predetermined amounts of rotation or pivoting of the steering wheel or handle.
These types of electric steering systems have become more popular recently. One reason is that these types of systems do not have a direct mechanical connection between the steering wheel or handle and the steering member. Thus, the movement or feeling of the steering wheel or handle is light, regardless of the speed of the watercraft. As such, it is easy for an operator to turn the steering wheel or handle at any operating speed.
During normal operation, however, changes in external forces applied to the boat, such as by waves and winds, are not transmitted to the steering wheel. Thus, drivers of such watercraft are not provided with the tactile signals corresponding to the changes in external forces that are normally provided to drivers of watercraft with conventional direct drive steering systems.
Other systems, such as that disclosed in Japanese Patent Document 2004-065689, have been proposed in which a sensor is provided for detecting the external forces applied to the boat. A reaction torque motor is used to apply torque to the steering device in response to the detected external force and control means are provided for converting the external force detected by the sensor to a value for torque, so that the reaction torque motor applies torque dependent on the external force to the steering device. With such a device, the operator can detect changes in the external force through the feeling of the forces applied to the steering wheel.